截取控件界面

介绍：
 做项目中，遇到需要截取界面图形的内容，查找了所有的Graphics函数，
 都没有此功能。只能用GDI32中的BitBlt来解决。
应用需要调用的函数
  class GDI32
 {
  [DllImport("GDI32.dll")]
  public static extern bool BitBlt(int hdcDest,int nXDest,int nYDest,
   int nWidth,int nHeight,int hdcSrc,
   int nXSrc,int nYSrc,int dwRop);
  [DllImport("GDI32.dll")]
  public static extern int CreateCompatibleBitmap(int hdc,int nWidth,
   int nHeight);
  [DllImport("GDI32.dll")]
  public static extern int CreateCompatibleDC(int hdc);
  [DllImport("GDI32.dll")]
  public static extern bool DeleteDC(int hdc);
  [DllImport("GDI32.dll")]
  public static extern bool DeleteObject(int hObject);
  [DllImport("GDI32.dll")]
  public static extern int GetDeviceCaps(int hdc,int nIndex);
  [DllImport("GDI32.dll")]
  public static extern int SelectObject(int hdc,int hgdiobj);

  
 
  public static void Cleanup(int hBitmap,int hdcSrc,int hdcDest)
  {
   // Release the device context resources back to the system
   User32.ReleaseDC(User32.GetDesktopWindow(),hdcSrc);
   GDI32.DeleteDC(hdcDest);
   GDI32.DeleteObject(hBitmap); 
  }
 
  public static void SaveImageAs(int hBitmap,string fileName,ImageFormat imageFormat)
  {
   // Create a bitmap from the Windows handle
   Bitmap image =
    new Bitmap(Image.FromHbitmap(new IntPtr(hBitmap)),
    Image.FromHbitmap(new IntPtr(hBitmap)).Width,
    Image.FromHbitmap(new IntPtr(hBitmap)).Height);
   image.Save(fileName,imageFormat);
  }    

 
 }
 class User32
 {
  [DllImport("User32.dll")]
  public static extern int GetDesktopWindow();
  [DllImport("User32.dll")]
  public static extern int GetWindowDC(int hWnd);
  [DllImport("User32.dll")]
  public static extern int ReleaseDC(int hWnd,int hDC);
 }
具体实现的方式
     和C++中的代码类似
        int hdcSrc = User32.GetWindowDC((int)this.control.Handle), // 获得控件的Handle
     hdcDest = GDI32.CreateCompatibleDC(hdcSrc), // 创建兼容DC
     hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc,
   this.control.Width,this.control.Height);//创建
     GDI32.SelectObject(hdcDest,hBitmap); // 选择
     GDI32.BitBlt(hdcDest,0,0,this.control.Width,
   this.control.Height,
   hdcSrc,0,0,0x00CC0020);//绘制图形
     Bitmap image = new Bitmap(Image.FromHbitmap(new IntPtr(hBitmap)),
   Image.FromHbitmap(new IntPtr(hBitmap)).Width,
   Image.FromHbitmap(new IntPtr(hBitmap)).Height);//转换为.net的Image类型
    GDI32.Cleanup(hBitmap,hdcSrc,hdcDest);//清除句柄